DISCUSSION - SR95

Table 7. Comparison of aggregate durabil-

ed averages in the same manner as that employed

ity* obtained using conventional freezethaw

for the absorption testing.

techniques to that using the cryogenic

A pore size distribution analysis yields much

method.

data, including total intrusion volume, and the

amount of intrusion within any diameter range, as

MDOT

CRREL

well as sample densities, median and average pore

MDOT CRREL

calc. equiv.

percent

rank

Sample

durability factor

passing

diameters and other information. The entire list of

data is not reproduced here, but pore size data

1

5

3987

100

0.60

abstracted from the results are provided in Table 6,

2

8

3704

100

1.07

where data are listed in order of increasing intru-

3

19

4204

100

33.31

4

20

4130

96

48.44

sion volume. Provided is the total amount of void

5

3

4205

88

0.10

space as well as the percentage of this space found

6

10

3632

81

1.43

within certain pore diameter ranges. Figure 2 plots

7

4014

77

0.89

intrusion volume against pore diameter. Clearly,

8

2

3666

75

0.08

samples 3593, 3595, 3791 and 4206 contain most of

9

4

4015

66

0.40

their pore volume below 5-m diameter (Fig. 2a),

10

16

4141

54

2.74

11

14

4033

50

2.35

whereas the remaining six samples contain pore

12

18

3595

41

3.94

sizes throughout the size range (Fig. 2b).

13

6

3990

32

0.76

14

17

3035

29

2.91

15

11

4206

27

1.53

DISCUSSION

16

13

3992

24

1.80

17

9

3791

22

1.13

The cryogenic freezethaw test was able to dis-

18

1

3989

10

0.03

tinguish one aggregate from another based on

19

15

3593

<10

2.49

frost damage. By freezethaw cycling aggregates

20

12

3991

<10

1.69

10 times between liquid nitrogen and hot water, it

* Expansion readings were omitted since their ranking

was possible to rank them according to freeze

is identical to that from the calculated equivalent dura-

thaw damage within an hour, as opposed to the

bility factor.

months that it now takes with current freezethaw

slags, 4204 and 4130. MDOT ranked these aggre-

test methods.

gates 3 and 4 while CRREL ranked them 19 and 20.

Table 7 and Figure 3 compare the cryogenic

The blast furnace slags performed very poorly

freezethaw results to those of MDOT. The first

in unconfined testing but quite well in the stan-

impression that one might gather from comparing

dard laboratory freezethaw test. The reason for

the individual rankings in the table is that the two

this may be explained by their wetting character-

freezethaw methods do not correlate well. This is

istics. Most researchers would agree that aggre-

most evident by looking at the results for the two

100